Had another friend test the same file on a MiBox and it played back without an issue.

what is the bitrate of the HEVC files you're trying to play on the ATV4? near 20mbit/s it seems to stutter in my experience.

if bitrate is low, perhaps it is due to some of the more expert settings in HEVC encoding and the software decoding (of the ATV4) struggles with fringe encoding settings regardless of bitrate. Just a thought.